Switchgear and similar electrical isolation equipment are highly regulated by industry standards (e.g., IEEE, ANSI, etc.). Among other things, these standards define the minimum clearance or spacing required in the absence of substantiating test documentation between exposed portions of adjacent conductors, such as adjacent electrical power buses, as well as from those conductors to ground for various voltage levels. This minimum clearance helps prevent electrical discharge between adjacent conductors and from a conductor to ground. The clearances are described in terms of direct or “strike” distances and linear surface or “tracking” distances. For example, in 15 kV switchgear, a minimum strike distance of at least 125 mm (4.9 inches) is typically required between the exposed portion of a conductor and ground.
Because of the industry-standard requirements, switchgear cabinets have heretofore needed to be a certain size or larger. Efforts to reduce switchgear cabinet sizes while satisfying the minimum clearance requirements have largely been unsuccessful. Additionally, in many switchgear applications, low-voltage current transformers (“CT”) are mounted around the electrical power buses to monitor and measure current flow. But low-voltage current transformers tend to be relatively large and bulky, which requires greater separation between the buses. The greater separation can be particularly problematic when deploying smaller footprint circuit breakers, such as the Evolis™ series of medium voltage circuit breakers from Schneider Electric USA, Inc. Due to their smaller size, these medium voltage circuit breakers have breaker terminals (e.g., upper or line side and lower or load side breaker terminals) that are located closer together so the breaker terminals are vertically offset from the power buses, which have a greater inter-bus separation. Furthermore, the power bus and breaker terminal can become extremely hot due to the large amounts of current flowing through them and heat sinks are typically needed to keep their temperature at or below a target level, which can add cost and complexity to the switchgear.
Thus, a need exists for a way to reduce the clearance needed between an electrical conductor and ground in switchgear and similar electrical isolation equipment while complying with industry-standard clearance requirements and also improving the heat sinking capability of such isolation equipment.